ABSTRACT
The course of the oculomotor nerve on the clivus was abnormal in a patient with petroclival
meningioma. He complained of gait disturbance. A gadolinium-enhanced magnetic resonance
image demonstrated a 4.4-cm enhancing mass in the petroclival region. The tumor was
removed via an anterior transpetrosal-transtentorial approach. Normally, the oculomotor
nerve originates from the brainstem and enters the oculomotor trigone. In this patient,
the oculomotor nerve entered the dura mater at the upper clivus, behind the posterior
clinoid process, and coursed parallel to the basilar artery. This entrance is lower
than the normal entry point of the oculomotor nerve. The abnormal entrance of the
oculomotor nerve may reflect an atypical developmental relationship among the cranial
nerves, meninges, and bones during embryogenesis.
KEYWORDS
Petroclival meningioma - anatomical variation - oculomotor nerve - microanatomy -
anterior transpetrosal-transtentorial approach